1. Field of the Invention
The present invention generally relates to an apparatus for forming a desired pattern and, more specifically, to a pattern forming apparatus using a technology of forming a desired pattern by pressing a mold on which the desired pattern is formed in advance to resin material (generally referred to as nanoimprint technology).
2. Description of the Related Art
In recent years, the width of pattern lines on integrated circuits has reduced in association with an increase in density and speed of semiconductor integrated circuits, and hence further enhancement of capabilities in a method of manufacturing a semiconductor is required. Therefore, a KrF laser (248 nm), an ArF laser (193 nm), and an F2 laser (157 nm) utilizing ultraviolet rays have been utilized in a photolithography machine used for forming a resist pattern in the lithographing step of a semiconductor manufacturing process, and shortening of wavelength of an exposure beam is in progress. At present, development of the photolithography machine using an EUV beam on the order of 10 nm in wavelength is in progress on a global scale.
Shortening the wavelength of the beam used for exposure is advantageous in that the resolution is increased. However, on the other hand, there arise problems such that the cost for development and manufacturing of materials for lenses, which constitutes an optical system, and the cost required for equipment for replacing the optical path with inert gas are high.
As a technology capable of forming fine resist patterns, there is a method in which an electron beam exposure machine using an electron beam. However, according to this technology, a pattern is directly drawn on a wafer, and hence it takes an extremely long time for exposing a single piece of wafer. Therefore, in the actual condition, it can only be applied to experimental manufacture or manufacture of device for specific use, which requires only a very small quantity, and hence cannot be applied to manufacture of devices which require mass-production, such as MPUs, memories, or system LSIs.
In recent years, in order to solve the above-described problems, there are proposed technologies capable of forming an extremely fine pattern at low cost. As one of these proposals, a nanoimprint technology has been a focus of attention (for example, see S. Y. Chou, et. al., Science, vol. 272, p. 85-87, 5 Apr. 1996).
The nanoimprint technology is a technology for transferring a pattern on the resist by pressing a mold 1311 as an original plate on which fine patterns are formed thereon by electron beam exposure against a wafer 1322 as a substrate on which resist 1321 is applied. FIG. 13A and FIG. 13B are explanatory drawing illustrating the outline of this technology.
FIG. 13A shows a case in which a pattern is not yet formed on the substrate, and FIG. 13B shows a case in which a pattern is already formed on the substrate, and a new pattern is to be formed on the pattern. After having formed the new pattern on the resist, etching process is preformed by RIE (Reactive Ion Etching) or the like, and then fine processing is effected on the substrate.
It is already proved that fine shapes on the order of 10 nm can be transferred with the nanoimprint technology. In particular, it attracts attention as manufacturing means for fine cyclic structure on a magnetic recording medium and hence research and development are in full force in various locations.
In the nanoimprint technology, since a pattern is formed by physically moving the resist when imprinting the mold against the substrate, environment may be made into a vacuum so as to prevent air bubbles from entering between the mold and the substrate. Also, a method of imprinting after enhancing flowability of the resist so that the resist can easily be flown upon imprinting by heating the resist in advance (so-called a thermal cycling method) or a method of using UV cure resin as the resist, exposing the resist in a state of being imprinted by a transparent mold, and releasing the mold after the resist has cured (so-called a photo-curing method) are proposed.
When patterning a fine shape of the magnetic recording medium, since precise alignment between the mold and the substrate is not necessary (FIG. 13A), nanoimprint can be applied relatively easily. However, when it is applied for manufacturing the semiconductor devices, for example, a highly integrated circuit such as an MPU or a memory, since the device structure is fabricated by superimposing the fine pattern on the position of the pattern which is formed in the previous process and transferring the same, precise alignment between the substrate as a base and the pattern on the mold is essential (FIG. 13B). When forming the pattern of 100 nm or below, accuracy on the order of 10 nm is required for alignment between the mold and the substrate.
When the mold is pressed against the substrate, the pattern on the mold is not transferred to the resist on the substrate unless the substrate and the surface of the mold come into close contact with each other. The parallelism between the surface of the mold (the surface having the transfer pattern formed thereon) and the surface of the substrate (having the resist applied thereon) may be displaced due to misalignment of the axis in the pressing direction even when the position alignment is performed with a position control mechanism in the apparatus before imprinting. Therefore, the nanoimprint apparatus in the related art has a mechanism to compensate misalignment in attitude between the surface of the mold and the substrate using a resilient leaf spring or the like.
In the structure of the nanoimprint apparatus in the related art, as shown in FIG. 14, when part of the surface of the mold 1411 is unevenly abutted against the substrate 1422 on which the resist 1421 is applied, the mold 1411 is rotated about the position at which the mold comes into contact with the resist 1421 first by an external force generated by a drive unit 1415, and hence the position of the mold may be displaced from the position where the mold is supposed to be aligned. Also, when a large load is exerted to the mold by the drive unit 1415, a resilient spring 1414 may be deformed and displace in the lateral direction, and hence a load to be exerted is limited.
In the structure of the nanoimprint apparatus in the related art, it is difficult to perform a mold pressing operation while maintaining the positions of, and the parallelism between, the mold and the substrate, and consequently, required specifications in terms of accuracy of alignment between the mold and the substrate at the time of the mold pressing operation cannot achieved. Therefore, it is difficult to apply the nanoimprint technology to highly integrated devices.